Hi SLCF, and welcome.
I wouldn't say that the feeling of brotherhood was fake, but it was conditional. It is built on a false premise. The idea is that extreme isolation and distancing is the only way to deal with those who are not in 'good standing.' The organization demands that its members act in ways totally anathema to the way they are used to treating each other, but also to go right back to being brothers and friends if a person's status reverts to 'good standing.' This is stressful, especially when we've been conditioned to be loving and brotherly and generous with one another.
And this conditioning can last a very long time. Glad to see you've come to terms with it and have freed yourself.